Facebook's $38 share price would make its deal to buy Instagram worth nearly $1.2 billion, up from the roughly $1 billion price the company announced in April . That's a nice little bump but the deal hasn't gone through given regulatory reviews. On top of that, we don't know the restrictions on the shares like when they vest or if they're subject to lock-up period. When Facebook agreed to buy Instagram, it said it would pay with $300 million in cash and 22,999,412 shares of stock. That stock is now worth nearly $874 million, creating a $1.17 billion price tag.

That’s a nice little bump but the deal hasn’t gone through given regulatory reviews. On top of that, we don’t know the restrictions on the shares like when they vest or if they’re subject to lock-up period. Plus, shares may pop tomorrow and their value will probably fluctuate a lot by the time six-month lock-up date hits. When Facebook agreed to buy Instagram, it said it would pay with $300 million in cash and 22,999,412 shares of stock. That stock is now worth nearly $874 million, creating a $1.17 billion price tag.

While the deal is ultimately expected to go through, a Facebook-Instagram acquisition poses several challenges for the FTC. For one, the FTC’s merger guidelines happen to focus a lot on pricing power, and how a merger would affect a company’s ability to raise prices and decrease output. But both Facebook and Instagram give their products away for free.

The other components of the FTC and Department of Justice’s guidelines have to do with market share. They’ll add up the square of different market shares for competing firms, creating a number called the Herfindahl-Hirschman Index. If it’s above 2500, then the market is highly concentrated. If it’s below 1500, then it’s unconcentrated.

But again, it’s not clear how this applies in a market where companies can rise and fall so quickly. Instagram basically appeared out of nowhere. It racked up nearly 40 million users in about 18 months. Plus, the time it takes for any given company to gain millions of daily active users is declining, partly because of the virality of the Facebook platform itself and then because the iOS and Android platforms are finally reaching scale.